Racial typologists have often claimed, with reason, that if human beings were just any biological species, the things we call "races" would be named as taxonomic subspecies. The fact that they're not (actually they have been, but the nomenclature is not generally recognized or accepted) is taken as evidence that the matter is so politically and socially charged as to prevent the normal exercise of taxonomic judgment. Those who, like the authors of this book, would like the entire notion of "race" to go away, have little choice but to acknowledge the point--and then point out that there is in fact no biological concept of the subspecies anyway, whether one is dealing with moths, kangaroos, or people. A subspecies is anything a taxonomist finds worthy of naming as such, and is thus entirely subjective, with no rigorous scientific criterion for taxonomic recognition. (This is a problem for endangered-species law too, insofar as it allows for protection of subspecies.) During the height of the neo-Darwinian synthesis, there was a tendency to view taxonomic subspecies as species in the making. With the advent of molecular genetics and especially genomics, it is now perfectly clear that taxonomic recognition cannot be taken as a good predictor of genetic differentiation. Some things that look very different are nearly identical genomically, and some things that are virtually identical in appearance show deep historical separation from their nearest relatives.
All of this is explained very well in this book, which makes the point (over and over again!) that our biological species is very young on a geologic time scale, that the processes of regional differentiation that led to the existence of what are commonly called "races" are perfectly normal and typical evolutionary processes, that the genetic differences among such "races" as quantifiable at the molecular level are minuscule and mostly apparently non-adaptive, and that (as "progressive" anthropologists have argued for several decades), "race" is at best a statistical concept that cannot be properly applied at the level of the individual. But as realists, the authors know that dismissing "race" as a biological construct will not make it go away as a sociocultural one. It merely weakens, if not removes, a prop commonly used by racial advocates of all stripes to support whatever claims they are making.
One of the best things in this book is its detailed dissection of racialized vs. personalized medicine in the light of contemporary genomics. I don't know a more lucid layman's explanation in print. Unfortunately, even this treatment is too technical for the average reader, whose eyes may glaze over after two or three pages of GWAS, SNPs, LD and AIMs. A pity, because even intellectuals like Henry Louis Gates have misunderstood and seriously overestimated the ability of these methods to tell us our ancestry and to define optimal medical treatments for our illnesses. Medical practitioners in general would do well to read Chapter 5, as this material is only now beginning to appear in medical-school curricula. Legal professionals also would benefit from it, both as it pertains to criminal forensics and, in the medical sphere, to personal injury/tort law.
I have two specific quibbles with the book. One: the discussion of ring species on pp.73-74 is garbled. The description of the California salamander example is both impossible to follow and geographically incorrect, and the claim that there are "many" such cases (p.73) is false, and belied by the fact that the California salamander case is the only one generally adduced in textbooks. A minor point, especially since the matter is largely irrelevant to human evolution. Two: While the authors seldom fail to identify or dissect the political biases of the racial typologists they discuss (the prime example being Carleton Coon), they do not do the same when citing or quoting authorities they agree with. Richard Lewontin, one of the most-frequently cited of these, is openly Marxist but is never identified as such. The late Stephen J. Gould, who did much to popularize the "mismeasure of man," was some sort of leftist, though just what kind and how much of one is still being debated years after his death. This is probably an unconscious slip on the part of the authors, but it can be interpreted badly. (The fact that they correctly identify the early anti-racist anthropologist Ashley Montagu as "ne Israel Ehrenberg" could be read by the very sensitive as somehow anti-Semitic, or tending to discredit his positions. That is clearly not their intent. Maybe they so identified him as a pre-emptive strike, lest they be accused of concealing his true ethnicity.) These quibbles merely underscore how politically touchy it is to say anything at all about race. This book says a lot.